1. Field of the Invention
This invention relates generally to cup packers for use in wellbore tools and, more specifically, formation interval straddle tools that are employed for earth formation zone fracturing or other formation treating operations in wellbores. More particularly, the invention relates to improved cup packers which resist the intrusion of sand and debris into their open end.
2. Description of Related Art
Cup packers used on formation interval straddle tools and other wellbore tools for oilfield applications are generally formed of hardened rubber materials and are of an open-ended design. During formation fracturing or treating operations when pressurized fracturing or treating fluids are pumped through the straddle tool to the formation zone to be fractured or treated, the open ends of such cup packers fill with the treating fluid which often has sand and debris entrained therein. If a xe2x80x9cscreenoutxe2x80x9d, during which sand is left within the straddled interval of the wellbore following treatment, occurs, the fluid within the straddled interval can become dehydrated forming a dense sand pack between the cup packers and within the open ends of the cup packers. The mechanical wedging of sand between the cup packers can result in high pulling forces during retrieval of the straddle tool following treatment of the formation. Additionally, sand wedged within the open ends of the cup packers may impair their ability to properly seal the interval straddled between the upper and lower packers of the straddle tool to sustain the necessary differential pressure during subsequent treatments of the formation.
Therefore, there is a need for an improved cup packer that resists the intrusion of sand and debris into its open end.
It is a principal feature of the present invention to provide a cup packer for use in wellbore tools and, more specifically, formation interval straddle tools, that resists the intrusion of sand and debris into its open end and thereby improves the operational characteristics and pressure-sealing performance of the wellbore tool.
Briefly, the invention is a cup packer wherein the open end is sealed or screened to prevent sand and debris intrusion therein.